Alcohol wine aroma

This process has found major application in the wine industry to control the alcohol content of wines (i.e. remove alcohol to the desired level). Wine is initially passed through the equipment at temperatures and pressures that primarily strip aroma components. The dearomatised wine is then passed a second time through the equipment at higher temperatures and vacuum to strip the desired amount of alcohol from the wine. The initially captured aroma fraction can then be added back to the reduced alcohol wine to produce the desired... 

Besides these simple fermentation alcohols, the yeast also forms higher alcohols as side products, "fusel oils," that have intense odors and play a role in wine aroma. Other components are carboxylic acids, such as tartaric and malic acids, that are important as "life-insurance" during aging of the wine. Some of the aromas perceived in wines stem from esters... 

The third and fourth influential factors on wine aroma chemistry arise from the problems caused by the matrix on both the isolation and preconcentration of molecules and on the sensory assessment of the role played by the impact odorants. The presence of major volatiles, such as ethanol and fusel alcohols, complicates the isolation of the other wine odorants, particularly of those present at low levels. This has a marked influence on the way in which the extracts for screening and for further qualitative or quantitative studies should be prepared. On the other hand, ethanol and the major fermentation volatiles have also a deep influence on the way in which the odor chemicals are released and perceived. 

Chalier et al. (2007), using mannoprotein at levels usually found in wines (150 mg/L), compared the effect of a whole mannoprotein extract (isolated from a synthetic medium subjected to alcoholic fermentation) to that of well characterized different mannoproteins fractions. From the four wine aroma compounds studied (isoamyl acetate, hexanol, ethyl hexanoate and /3-ionone), all except isoamyl acetate showed a decrease in volatility (up to 80%) when mannoproteins were present (Fig. 8F.3). They suggested that both the glycosidic and the peptidic parts of these macromolecules may be responsible for the interaction. They also found that the interactions of the whole mannoprotein extract Vs. mannoprotein fractions were different, suggesting that the conformational and compositional structure of these... 

It is interesting to note that in fermented products the same alcohols always form, even if different sources of nitrogen, but not singular aminoacids, are available. Ketoacids can also be directly reduced to hydroxyacids such as lactic, 2-hydroxy-3-methyl butyric, 2-hydroxy-3-methyl pentanoic, 2-hydroxy-4-methyl pentanoic, 2-hydroxy-3-phenyl propionic and 2-hydroxy glutaric acids. The corresponding ethyl esters can dramatically influence the wine aroma. 

Although there are strain specific variations, the principle higher alcohols involved in wine aroma ares 1-propanol, 2-methyl-l-propanol, 1-butanol, 2-phenylethanol, 2-methyl-l-butanol, 3-methyl-l-butanol, 1-hexanol, l-octanol(23). These are likely to be derived in part, from amino acids via the Erhlich pathway. Organic Acids present ares acetic, isobutyric, isovaleric, hexanoic, and decanoic(24). Aldehydes present ares acetaldehyde, isobutyraldehyde,... 

The main volatiles in wines are the higher aliphatic alcohols, ethyl esters, and acetates formed from yeasts during fermentation. Acetates are very important flavors characterized by fruity notes, C4-Ci0 fatty acid ethyl esters manly confer fruity scents to the wine. Other wine aroma compounds are C6 alcohols, such as 1-hexanol and cis- and trans-3-hexen-l-ol, 2-phenylethanol, and 2-phenylethyl acetate. Contents of these compounds in wine are linked to the winemaking processes used fermentation temperature, yeast strain type, nitrogen level in must available for yeasts during fermentation, clarification of wine (Rapp and Versini, 1991). Much literature on the wine aroma compounds was reported in reviews by Schreier (1979) and Rapp (1988). 

These alcohols and their esters have intense odors that play a role in wine aromas. The main higher fermentation alcohols, components of Fusel oils, are isobutyl (methyl-2-propanol-l) and amyl alcohols (a mixture of methyl-2-butanol-l and methyl-3-butanol-l). At low concentrations (less than 300 mg/1), they contribute to a wine s aromatic complexity. At higher levels, their penetrating odors mask the wine s aromatic finesse. Acetic esters of these alcohols, especially isoamyl acetate, have a banana odor that may play a positive role in the aroma of some young red wines (primeur or nouveau). 

The free volatile compounds of wines were extracted with dichloromethane. Representative wine aroma extracts for chemical and olfactory analysis were obtained using this solvent. Fig. 1 is the TIC of free volatile compounds of Rojal wines detected by SPE-GC-MS. Quantitative data of the volatile compormds found in free aroma fraction of the young red wines from Rojal grape variety are shown in Tables 1 and 2. The data are expressed as means (pg/1) of the GC-MS analyses of duplicate extractions and they correspond to the average of the analyzed wines. Improvement in the analytical method used to extract the volatile compounds from these wines has allowed us to identify and quantify 80 free volatile compounds in Rojal red wines including alcohols, esters, acids, terpenes, C13 noiisoprenoids, Ce compounds and benzenic compounds. They have been positively identified and quantitatively determined. 

Benzene compounds. Benzene compounds are an important group in varietal aroma, abimdant in wines, including aromatic alcohols, aldehydes, volatile phenols and shikimic acid derivates. The volatile phenols in wines can come from grapes, both as free and bound aroma, or be generated during the alcoholic fermentation by chemical reactions such as phenolic add degradation, or in the case of vinylphenols due to brettanomyces contamination (Suarez et al., 2007). Volatile phenols are considered characteristic components of wine aroma, although their influence on the final product may be positive or... 

The involvement of yeast hulls in fermentation processes is also accompanied by variation in the concentration of secondary products (higher alcohols, fatty acids and their esters). As a result, wine aromas and tastes can be modified. All operations that affect fermentation kinetics affect the wine—temperature, oxygenation, addition of ammonium salts, etc.—and yeast hulls have no more of an impact on the fermentation than these other factors, and certainly less than temperature. 

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